* Low Transmission Fluid: This is the most common and easiest to check. Low fluid can cause erratic shifting and slipping, leading to the symptoms you describe. Check the transmission fluid level *while the engine is running* and warmed up. The level should be in the proper range on the dipstick. Also inspect the fluid for color and condition; burnt or dark brown fluid indicates a serious problem.
* Failing Transmission Solenoids: These electrical components control the flow of transmission fluid, directing it to the correct clutches and bands for each gear. A failing solenoid can cause inconsistent shifting, including slipping into neutral. This often presents as intermittent problems, making diagnosis trickier.
* Worn Transmission Bands or Clutches: These components within the transmission engage and disengage gears. Wear and tear, especially with age, can lead to slipping and difficulty maintaining gear engagement. This is a more serious issue requiring transmission repair or rebuild.
* Torque Converter Problems: The torque converter connects the engine to the transmission. A malfunctioning torque converter can cause slipping and erratic shifting, especially at low speeds. A failing torque converter will often exhibit shuddering or slipping.
* Shift Linkage Issues (less likely): While less probable given the description, a problem with the linkage connecting the shifter to the transmission could theoretically cause this, but it's less likely to manifest as sudden neutral shifting.
* Transmission Control Module (TCM) Problems: The TCM is the computer that controls the transmission. A faulty TCM can lead to a variety of shifting problems. This is less common but possible.
Troubleshooting Steps:
1. Check the transmission fluid: This is the absolute first step. Low or dirty fluid is a major culprit and easily addressed.
2. Inspect for leaks: Look under the van for any signs of transmission fluid leaks.
3. Have a professional diagnose the problem: A mechanic can perform a more thorough diagnosis, including checking the solenoids, testing the TCM, and assessing the internal condition of the transmission. They have the tools to test fluid pressure and other critical parameters.
Ignoring the issue can lead to further transmission damage, resulting in costly repairs or a complete transmission replacement. It's crucial to address this problem promptly. Don't continue driving the van extensively until the cause has been identified and resolved.
